The invention relates to mechanical linkages for translating movement between a first and a second member and which incorporate an override mechanism which enables movement of a third member to affect the translational movement between the first and second members. In one example of the invention to be described in more detail below, the mechanism is used for controlling the fuel supply to an engine such as the engine of a vehicle. Thus, in this example, the "first member" is a member whose movement is controlled by the vehicle driver (for example, the throttle or accelerator pedal) and the "second member" is a member connected to the engine's carburetor or diesel fuel injection pump and thus controls the fuel supply to the engine. The "third member" is a member controlled by an engine speed controlling or limiting system and enables the latter to "override" the driver's setting of the fuel supply; thus, the control or limiting system may thereby shut off or reduce the fuel supply in opposition to the action of the driver.